Cloud Computing Project High Level Design Document

Transcription

1 Cloud Computing Project High Level Design Document Date : 2 nd October, 2010 Team and Project Details Project Distributed Rendering of 3D Images Team Number 9 Team Name Foobar Team Members Aditya Deshpande ( ) Ishan Misra ( ) Final Approach Overview :- The project deals with the following ascpects 1. Splitting a 3D volume data-set of a static image, available as a set of small triangles(or other graphics primitives), eg. PLYfile, into multiple chunks. 2. Processing each chunk separately using a graphics API to generate intermediate frame buffers. 3. Combining all the frame buffers generated to create the final frame buffer for the input image, which can then be directly rendered to any display or stored as a 2D image. Detailed Approach :- 1. Suppose the input file is a PLYfile ( 2. The preprocessing involves reading the header of this file to identify parameters such as the header length, number of vertices, number of graphics primitives and other auxiliary information about colors and textures.

2 3. A map-reduce job is launched which uses the above header information to separate the vertex information and the primitive (shape) information and outputs them separately. This modularity helps handle other input data formats apart from ply. Pseudo Code : (Set #reduce tasks = 2) Mapper (key :: lineoff-set, value :: <line data>) linenum = getlinenumber(lineoff-set) if(linenum > headerlength && linenum < headerlength + numvertices) Emit(key :: Vertex, value :: <line data> ) else if (linenum > headerlength) Emit(key :: Primitive, value :: <line data> ) Reducer( key :: <type ( Vertex / Primitive )>, value :: <line data> ) Emit (key :: <type ( Vertex / Primitive )>, value :: <line data>) 4. A second map reduce job is launched with the above primitive files as input. The vertex files are global to all the map and reduce tasks. 5. The map task gets n primitives as inputs and it generates a frame buffer. It emits the key-value pair consisting of <pixel window co-ordinates, depth and color information>

3 Pseudo Code : Mapper(key :: lineoff-set, value :: <line data>) count = getcount() If( count <= n) vertexdata = getvertexdata(<line data>) render(vertexdata) else writetoframebuffer() foreach(pixeldata from framebuffer) depthandotherdata=getdepthandother (pixeldata) coorddata = getcoorddata(pixeldata) emit(key :: coorddata, value :: depthandotherdata ) Reducer( key :: <coorddata> value :: <otherdata>) coord= getminvalue(depth(allvalues)) emit(coorddata,otherdata(coord)) 6. The output of the above can directly be rendered using a gldrawpixels() like call to a standard graphics API to render the final image. Justification of Approach :

4 1. The output image is a completely accurate representation (within allowed errors introduced by depth buffering hardware)of the input data-set and also mirrors the output produced by rendering done on a single machine. 2. The processing on each node is designed such that view frustum culling, hidden surface determination and rasterization are done very efficiently by the graphics pipeline through graphics hardware support. 3. The depth buffering manipulations are done on a given pixel over a set of frame buffers. This is suitable to the map-reduce, as we can have pixel as the key and the data for this particular pixel in each of the frame buffer as the value. 4. The above pseudo code shows that our approach blendes well within the map reduce framework. Functionalities to be offered 1. Scales well for reasonably large data-sets. 2. Using the modular design of the code, we can adapt it to various other input formats. 3. Portable to multiple platforms. 4. If available and pre-configured, rendering is accelerated by the graphics hardware. Technologies / Frameworks / Tools and API s 1. Java : To make it compatible with Hadoop API. 2. Hadoop : Distributed Computing Framework 3. JOGL : OpenGL compatible Graphics API in Java.

5 Architecture Diagram(s) Input : PLYfile ply element vertex 9200 property float x property float y property float z element face property list uchar int vertex_indices Pre Processing Header Information : length 06, Vertices 9200, Primitives (2) (1) Map Task Mapper (key :: lineoff-set, value :: <line data>) Reduce Tasks (#reduce Tasks = 2) (3) (4) Reducer( key :: <type ( Vertex / Primitive )>, value :: <line data> ) (5) Vertex Data (GLOBAL to all map tasks) Vertex, <data> Vertex, , , Vertex, Primitive Data (Split into CHUNKS ) Primitive,<data> Primitive, 3,4,5 Primitive, Map Task Mapper (key :: lineoff-set, value :: <line data>) (6) Intermediate Frame Buffer <Co-ordinates>, <other data> Reduce Tasks (8) Reducer( key :: <coorddata> value :: <otherdata>) (7) Final Frame Buffer <Co-ordinates>, <other data> < (23, 24), (0.000, 0.000, 0.000)>